Muscle Fibers

Muscle Fibers

Muscle Cells

Epimysium

dense irregular CT that surrounds whole muscle

Perimysium

dense irregular CT that surrounds groups of muscle fibers called fascicles

Endomysium

fine areolar CT that surrounds each individual muscle fiber

Sarcolemma

Plasma membrane of a muscle fiber

Sarcoplasm

cytoplasm of a muscle fiber

Myofibrils

rod-like organelles made of contractile filaments

Sarcoplasmic Reticulum

stores and releases calcium to signal muscle contraction

T-Tubules

conduct impulses throughout the muscle cell

Sarcomere

the smallest contractile unit of muscle tissue, on myofibrils

A band

myosin filaments (darker region)

M Line

middle of sarcomere

I band

actin filaments (lighter region)

Z Disc

anchors the thin filaments

H Zone

shortens during muscle contraction (sorrounds M Line in middle)

Motor End Plate

folded area where the muscle and neuron communicate

Acetylcholinesterase

(enzyme) breaks down acetylcholine in the synaptic gap

Cross Bridge Formation

myosin head attaches to actin 1

Power Stroke

myosin head pulls actin toward M Line, ADP+P released 2

Cross Bridge Detachment

Another ATP binds to myosin, heads detach (requires ATP) 3

Cocking Myosin Head

ATP hydrolyzed, energy is released and

myosin head returns to “cocked” position 4